1. Field of the Invention
The present invention relates to a radio base station in which radio communication modems are mounted for communicating with mobile stations in a mobile communication system, to a fault recovery method for the radio communication modems, and to a mobile communication system that employs this radio base station and fault recovery method.
2. Description of the Related Art
We first refer to FIGS. 1 and 2 to explain the construction of a typical mobile communication system, for example, a mobile communication system that adopts a CDMA (Code Division Multiple Access) communication method.
Referring to FIG. 1, the mobile communication system is configured such that a plurality of radio base station controllers 2-1 and 2-2 are connected to one maintenance monitor device 1, a plurality of radio base stations 3 (3-1, 3-2, and 3-3) are connected to one radio base station controller 2-1, and a plurality of mobile stations 4 (4-1, 4-2, 4-3, 4-4, 4-5, and 4-6) are present within the area of one radio base station 3. Maintenance monitor device 1 is connected by wire lines to each radio base station controller 2, radio base station controllers 2 are each connected to radio base stations 3 by wire lines, and radio base stations 3 are each connected to mobile stations 4 by radio lines. Referring to FIG. 2, each radio base station 3 is of a construction for providing radio communication service in an area that is divided into three sectors a, b, and r; and realizing signal transceiving of radio sections with each mobile station 4 in sector units.
Each radio base station 3 is provided with a plurality of radio transceivers and signal converters. Radio transceivers perform radio communication with mobile stations 4 in sector and frequency units. The signal converters each include a plurality of radio communication modems for carrying out modulation (spreading) and demodulation (despreading) in the CDMA communication method, these being the signal conversion processes of each of the communication channel signals to mobile stations 4 that have passed through the radio transceivers. These signal converters have a card structure that can be attached by means of connectors to the main unit in a freely removable state. Thus, one signal converter card performs call connections with a number of mobile stations 4 equal to the number of mounted radio communication modems.
Each time radio base station controller 2 experiences a call connection failure in this type of mobile communication system, maintenance monitor device 1 is supplied with the cause of the call connection failure and the number of the radio communication modem to which the call connection was assigned at the time of the failure, whereby maintenance personnel can ascertain the state of the radio communication modems that is loaded in radio base station 3.
The above-described system of the prior art suffers from two problems. First, it is difficult to determine whether a call connection failure is due to a radio section or to a fault of a radio communication modem. In addition, the connection of a plurality of radio base stations to a single maintenance monitor device means that a large number of reports are received regarding the causes of call connection failures that occur in each radio base station, and the maintenance personnel therefore needed considerable time to fully comprehend the faulty state of a radio communication modem.
There is the additional problem that a plurality of call connections have to be performed to specify whether a problem is actually occurring in a radio communication modem, and as a result, even when a problem is occurring in a radio communication modem, the radio communication modem in which a problem is occurring has to be used to perform call connections.